1. Field of the Invention
The present invention relates to an optical touch system and method.
2. Description of the Related Art
FIG. 1 illustrates a prior art infrared touch-sensing system 1. As shown in FIG. 1, the prior art infrared touch-sensing system 1 includes a touch surface 10, a plurality of X-axial infrared-emitting elements 122, a plurality of X-axial infrared-receiving elements 132, a plurality of Y-axial infrared-emitting elements 142 and a plurality of Y-axial infrared-receiving elements 152. The X-axial infrared-emitting elements 122 are in one-to-one correspondence with the X-axial infrared-receiving elements 132, and the Y-axial infrared-emitting elements 142 are in one-to-one correspondence with the Y-axial infrared-receiving elements 152, thereby forming sensing paths (as illustrated in dashed lines) that cross each other. In this way, a sensing grid is formed over the touch surface 11. When an object O1 approaches the touch surface 11, the object O1 blocks a sensing path in the sensing grid, which corresponds to a position x4 on the X-axis and a sensing path in the sensing grid, which corresponds to a position y5 on the Y-axis. Therefore, the X-axial infrared-receiving element 132 at the position x4 receives infrared with less intensity Ix in comparison to the X-axial infrared-receiving element 132 whose corresponding sensing paths are not blocked. Similarly, the Y-axial infrared-receiving element 152 at the position y5 receives infrared with less intensity Iy in comparison to the Y-axial infrared-receiving elements 152 whose corresponding sensing paths are not blocked. Because the intensities of infrared received by the infrared-receiving element 132 corresponding to the position x4 and the infrared-receiving element 152 corresponding to the position y5 are significantly lower, it can be derived that a touch position of the object O1 is located at the position (x4, y5).
However, the prior art infrared touch-sensing system 1 requires that the infrared-emitting elements 122 or 142 should be in one-to-one correspondence with the infrared-receiving elements 132 or 152, and that is the infrared-emitting elements 122 or 142 should be a narrow beam light source instead of a regular scattering light source so that the infrared-receiving elements 132 or 152 will only receive the light beams emitted by the corresponding infrared-emitting elements 122 or 142. Otherwise, the blocked sensing path cannot be accurately determined. However, it is difficult to confine the light beam emitted by an infrared-emitting element 122 or 142 to be received only by a single infrared-receiving element 132 or 152. Hence, an infrared-receiving element 122 or 142 of which the sensing path is blocked may receive infrared emitted from neighboring infrared-emitting elements 132 or 152, causing the output coordinate to be inaccurate. In addition, the situation is compounded with an object O2 being located between positions x2 and x3 because the sensing paths corresponding to positions x2 and x3 are not completely blocked. With sensing paths that are not completely blocked, the position of the object will be more difficult to accurately determine. To reduce the above-mentioned negative effects, the prior art infrared touch-sensing system 1 mostly adopts a scanning method that enables the infrared-emitting elements 122 and 142 in sequence, so as to reduce interference. Nevertheless, this method still requires a narrow beam light source and may result in a longer touch-sensing response time. Moreover, in multi-touch applications, when there are a plurality of objects O1 and O2 approaching the touch surface 11 simultaneously, the prior art infrared touch-sensing system 1 cannot differentiate whether the touch positions of the object O1 and the object O2 are (x4, y5) and (x2+Δx, y2), or (x2+Δx, y5) and (x4, y2).
Therefore, it is desirable that an optical touch system and method can more accurately and easily determine touch positions of a plurality of objects.